Analyzing noise-induced tracking errors in control systems with saturation: A stochastic linearization approach

Noise Induced Tracking Error (NITE) refers to the tracking error of the mean of the output in feedback control systems with nonlinear instrumentation subject to zero-mean measurement noise. Most of the previous work rely on the stochastic averaging for NITE analysis, the validity of which requires that the bandwidth of the zero mean measurement noise is much higher than that of the system. This is because the results obtained by stochastic averaging are asymptotic with respect to the noise bandwidth. Due to the asymptotic nature of the analysis tool, it is not straightforward to provide a quantitative argument for high bandwidth. An alternative method in the literature that can analyze NITE is stochastic linearization for random input, which is analogous to the well known describing function approach for sinusoidal input. Unlike stochastic averaging, stochastic linearization is not an asymptotic approximation. Therefore, analysis can be carried out for any given noise bandwidth. We carry out NITE analysis using stochastic linearization for a class of LPNI systems that are prone to NITE; identify the system conditions under which the averaging analysis of NITE may yield inaccurate results for a finite noise bandwidth; and prove that the results from the two methods agree as the noise bandwidth approaches infinity. In addition, an existing NITE mitigation strategy is extended based on the proposed method. Numerical examples are given to illustrate the results.     

Non-fragile quantized H∞ output feedback control for nonlinear systems with quantized inputs and outputs

This paper is concerned with non-fragile $H_{\infty }$ control problems for a class of continuous-time nonlinear systems with unknown nonlinearity and quantized inputs and outputs. The construction of both static output feedback (SOF) and observer-based output feedback (OBOF) control laws in the presence of additive interval-bounded controller coefficient variations can be divided into two parts, linear and nonlinear parts. The linear part plays a role in achieving the $H_{\infty }$ performance, while the nonlinear part is used to reduce the quantization effect. However, it should be pointed out that the effect of input and output quantization can be eliminated fully for SOF case by requiring knowledge of all signs of the states, but only the effect of input quantization can be eliminated for OBOF case. It is worth mentioning that three novel alternative methods with strict linear matrix inequality (LMI) conditions are proposed to design both SOF and OBOF controllers. In particular, these three new methods do not introduce any other auxiliary constraints as many existing results do where a matrix equality constraint between system matrix and Lyapunov matrix is often inserted. Finally, the effectiveness and advantages of the proposed control methods are demonstrated by a numerical example.     

The relationship between risetime,settling time,bandwidth and Q in certain distributed microwave networks

Relationships between risetime, settling time, bandwidth and Q are presented for the class of TEM-mode delay line filters whose impulsive response is a train of uniformly spaced, but unequally weighted impulses. Conventional measures of bandwidth for these systems are undefined because the energy spectrum is a periodic function of frequency. It is shown, however, that with careful interpretation one may derive a useful inverse relationship between bandwidth and risetime via a suitably modified autocorrelation function; the relationship is a risetime-bandwidth product equaling a constant derived by an equivalent area measure. It is also shown that a useful estimate of the settling time of a system can be obtained in terms of the moments of the impulse response which weight heavily the contributions of the remote time domain residues. Examples are presented to demonstrate the application of the theory.     

Convexity of the Energy Domain

A basic theorem describing the convexity of the energy domain for the general family of linear time-invariant (active or passive, reciprocal or non-reciprocal, lumped or distributed, single variable or multivariable) physical system {T} is proved.Theorem: Let F = P + jQ represent the complex energy associated with any linear physical system T (n-port). For any specified excitation of frequency s and the family of constant energy content input signals {i:∥i∥= constant}, the point F describes a convex domain in the {P;Q} plane.Part I contains a mathematical and a network theoretic proof of the foregoing theorem. In Part II the geometric nature of the energy loci for the two-ports is examined. It is shown that for all two-ports with double eigenvalves the energy domain is circular. For two-ports with distinct eigenvalves, the convex energy domain is an ellipse. The geometric characterization of this elliptic domain is examined and examples verified by computer.The concept of convexity is frequently exploited in optimization of energy in electric power system and quadratic cost functions in control theory. In this respect the central theorem of this paper, its proof and geometric ramifications should prove to be of basic interest for all linear systems.     

Robust quantized consensus of discrete multi-agent systems under input saturation

In this paper, we consider the quantized consensus problem of multiple discrete-time integrator agents which suffer from input saturation. As agents transmit state information through communication networks with limited bandwidth, the states of agents have to be quantized into a finite number of bits before transmission. To handle this quantized consensus problem, we introduce an internal time-varying saturation function into the controllers of all agents and ensure that the range of the state of each agent can be known in advance by its neighboring agents. Based on such shared state range information, we construct a quantized consensus protocol which implements a finite-bit quantization strategy to all states of agents and can guarantee the achievement of the asymptotic consensus under any given input saturation threshold. Such desired consensus can be guaranteed at as low bit rate as 1 bit per time step for each agent. Moreover, we can place an upper bound on the convergence rate of the consensus error of agents. We further improve that quantized consensus protocol to a robust version whose parameters are determined with only an upper bound on the number of agents and does not require any more global information of the inter-agent network. Simulations are done to confirm the effectiveness of our quantized consensus protocols.     

Fixed-time scaled consensus of multi-agent systems with input delay

The design of fixed-time scaled consensus protocol for multi-agent systems with input delay is developed in this article. First, by virtue of Artstein model reduction method, the time-delay system is converted into a delay-free one. Then, two novel controllers are designed such that the fixed-time scaled consensus of multi-agent systems can be realized for the undirected and directed topology, respectively. Sufficient conditions are derived to guarantee that all agents converge to the assigned ratios instead of the same value under any bounded input delay. Besides, an explicit estimate can be given for the uniform convergence time independent of the initial conditions. Moreover, it is proved that the convergence value of the system is not affected by the initial states of agents any more, but only related to initial states of the virtual agents set in advance. Finally, numerical simulations are given to demonstrate the feasibility of the proposed algorithms.     

雷电迎面先导过程中瞬态电磁场的检测与分析

雷电是大气运动的一种放电现象.雷电释放能量很大,它在短时间内可以释放数百兆焦耳的巨大能量;除了直接雷击带来的危害之外,同时引发强烈的雷电电磁脉冲,对雷电附近的电力系统以及通讯设备等都会造成极大的危害。要控制雷电的发展方向,影响雷电形成的初级阶段是一个重要的突破口。为了进一步了解雷电初级阶段产生的电磁场分布以及将来设计新型抗雷电电磁干扰系统打下基础,文章总结了近年来电磁场的检测方法与分析方法。     

Circuit state analysis using chaotic signal excitation

A new testing method for analog circuit is proposed in this paper. A low-pass Butterworth filter is taken as the typical system under test (SUT) since the analog circuits in different types of electronic systems can be regarded as the low-, band- or high-pass active (passive) filters. The chaotic signal, which is generated by an improved Chua's circuit, is employed as the excitation signal of SUT. The SUT is a “narrowband” system compared with the bandwidth of input signal, whose state is analyzed with an error-tracking approach. The experimental result depicts that this testing method can efficiently detect the change of the circuit parameter. Besides, another eight features are extracted from the output signal of SUT for analyzing the SUT states. A discussion is made for comparing the effectiveness of each feature according to the testing results.     

中国产业部门的能耗强度特征及节能减排的分类实现路径

产品生产过程中除了直接消耗能源之外,还有通过中间产品投入而产生的间接能源消耗。因此,仅仅依靠提高能源利用效率来进行节能减排,其作用是有限的,必须要综合考虑生产过程中对能源、物质投入的需求。本文通过投入产出方法分析了我国2002年各个产品部门单位产值的直接和间接能源消耗,发现大部分产品部门单位产值的间接能耗都大于直接能耗,即生产过程中的大量物质投入导致了大量的间接能源消耗。因此,要实现节能减排的目标,直接能耗高的部门要提高其能源利用效率,而间接能耗高的部门要提高其中间投入的利用效率,同时要推动低能耗的服务业的发展以及在全社会推进“减物质化”发展,减少物质消耗而导致的间接能源消耗,而这需要人力资本的大量积累以及服务业的发展。     

基于模型驱动技术的XML表单开发

采用数据驱动的方法来构建标准化格式支持的、易理解的、可移植的表单。任何软件系统的开发都需要创建表单来收集用户输入的数据,表单在用户输入和软件系统的业务流程中担当了关键角色。     

Doppler invariant pulse compressors

A pulse compressor is utilized in many aspects of signal processing. Compression is usually accomplished by using special matched-filter-signal pairs. An alternative method takes advantage of the fact that any linear dynamic system can be excited to produce a time-limited output. Accordingly for a given dynamic system a synthesis procedure is provided for stepwise-constant input pulses evoking a time-limited response. Pairing the signal and system carefully leads to pulse compression. The Doppler invariant pulse compression is an important special case. Many examples are given.     

A dissipativity-based approach to traffic signal control for an over-saturated intersection

In this paper, using the energy concept, the control of traffic flow by traffic lights on an over-saturated single intersection is addressed. By regarding the flow entry of vehicles as the energy stored in the system, we show that the dissipative system theory can be applied. As a result, a state feedback control law is found in terms of the solution of an associated dissipation equation that renders the system non-accumulative, i.e., to get out of the over-saturation situation. The results of the simulations indicate that our control strategy guarantees a high degree of control benefit.     

波函数塌缩问题及物理量期望值表达式的讨论

为把波函数的塌缩与实验观测联系起来,通过“在一个足够长的时间段内空间某点位置通过实验获得的某物理量观测数据的个数与波函数在空间该点的概率成正比”的假设,得到了物理量平均值的表达式,给出了一个意义更加明确的物理量观测值的数学表达式。     

Finite-time non-fragile l2−l∞ control for jumping stochastic systems subject to input constraints via an event-triggered mechanism

In the work, the finite-time non-fragile $l_2?l_{\infty }$ control problem for jumping stochastic systems with input constraints is addressed. An event-triggered mechanism is introduced to reduce the burden of the data communications. Our goal is to design a controller which makes sure that the underlying closed-loop system could be stochastically finite-time bounded at a specified level of $l_2?l_{\infty }$ performance. By using the finite-time analysis theory, some sufficient conditions are proposed for the existence of such a desired controller. The availability of the developed method is finally explained by an illustrated example.     

User-satisfaction based bandwidth allocation for transmission of multiple sources of human perceptual data

In recent years, more and more point-to-point communication systems involve simultaneous transmission of multiple sources of human perceptual data over a single communication medium. For example, in a teleoperation system or a telerobotic system, streams of video, audio, and haptic data need to be sent from a field place to a remote human operator. Each type of data demands a certain range of transmission rate. This creates conflicts among these data when the available bandwidth is limited.In this paper we study the bandwidth allocation for multiple sources of human perceptual data transmitted over a rate-limited communication channel. We aim to maximize the overall user satisfaction in the data transmission, and formulate an optimization problem for the bandwidth allocation. Using either the logarithmic or exponential form of human perceptual satisfaction function, we are able to derive closed-form solutions for the optimization problem. We show that the optimal bandwidth allocation for each type of data is piecewise linear with respect to the total available bandwidth.     

Reliable control based on dual control for ARMAX system with abrupt faults

This paper studies the reliable control problem for abrupt faults of autoregressive moving average with exogenous input (ARMAX) system. A set of models are used to cover the potential dynamics of the system and for each model minimum variance control (MVC) is designed. By taking the a-posteriori probabilities of models as weight coefficients, a multi-model reliable control (MMRC) is proposed. If the system is normal, MMRC is MVC. When faults occur, the controller can quickly learn the true model of system and degenerate into the corresponding MVC by adjusting weight coefficients, which ensures the acceptable performance of the system. The effectiveness of MMRC is verified by a numerical simulation. In addition, since MMRC is a fusion of control law of each model, it indicates that soft switching is implemented and the jitter to system due to hard switching can be avoided.     

一种无线电能传输系统的设计

无线电能传输是通过电磁波进行电力传输,从而省去电源线和插座的一种新型电源。本设计的无线电能传输系统采用电磁感应方式,充分结合了磁耦合技术和开关电源技术。系统分为无线发射部分和接收部分,在12V电源供电下,3mm距离耦合时效率达到了67%,输出功率1.16W。整个电路结构简单,工作稳定,经过检验在6cm范围内能够点亮发光二极管,达到了实际应用水平。